Saving address data after reload if user forgets one oh the required fields

Saving address data after reload if user forgets one of the required fields

I guess this is more of a usability-friendly kind of question:
(and please excuse me for being totally blunt — i'm not a programmer)
we're beta testing our new website and want to include your shopping cart in it
and i ran into a following problem:
we want to allow users to purchase without registration
and all fields in the billing adress except "State/Bundesland" are required
when user "forgets" to fill out one of the required fields and presses "Continue/Weiter"
he/she is returned to totally empty form again
(this applies for both cases with billing or billing+different shipping address)

Is there a way to save the already entered user details in such a case???